The invention relates to a method, a phase grating and a device intended for analyzing the wave surface of a light beam for an optical control. This type of analysis is intended for controlling optical elements, for the qualification of optical devices as well as for the operation of deformable optical elements used in active or adaptative optics. It also makes it possible to study non directly measurable physical phenomena, such as the variations in the optical index inside turbulent media which can be met when going through the terrestrial atmosphere or in a wind tunnel pipe. It is also used for controlling the flatness of electronic components, for example matrix focal planes, as well as for shaping power laser beams.